1. Field of the Invention
This invention relates to water-activated batteries, that is so-called deferred action batteries that can be stored dry for prolonged periods and then activated when water or similar liquid is allowed to come in contact with the electrodes. Such batteries find use on life rafts, survival kits and the like to power a signal light for use in an emergency.
2. Prior Art
Khasin U.S. Pat. No. 5,424,147 discloses a water activated battery in which the cathode comprises a skeletal frame including conductive metal and having a portion of its surface area formed as open spaces, and further comprising a heat pressed rigid static bed of active cathode material encompassing the frame and formed of cuprous chloride, sulfur, carbon and a water ionizable salt. The only water ionizable salts disclosed are sodium chloride and calcium sulfate, and a preference is expressed for salts that are sparingly soluble in water having a solubility of less than 50 grams per liter (see col 3 lines 15-16).
McCarter U.S. Pat. No. 5,395,707 discloses a water-activated battery with a cuprous iodide cathode, and a magnesium anode that can contain minor amounts of zinc as an alloy constituent, stated to be functionally comparable to a lead chloride electrode water activated battery.
Rao U.S. Pat. No. 5,225,291 discloses a water actuated battery including a plurality of electrochemical cells including a "hybrid cathode member" which is described (col 3 lines 21-28) as "formed of a material exhibiting inertness (low corrosion) such as nickel, stainless steel, titanium, graphite, carbon, etc., suitably subjected to catalytic activation.
Japan 53-4824 (Yuasa 1978) discloses a sea water battery of specified design in which the cathode contains silver chloride, copper chloride, copper sulphate or manganese dioxide. There is no mention in the English language abstract of graphite as a constituent of the cathode.
Japan 47-43887 (Yuasa 1972) discloses a magnesium salt-water cell including a silver chloride, copper chloride, manganese dioxide, air, etc., cathode and further containing a crystalline or glassy water-soluble weak acid or its anhydride. The only specific "weak acid or anhydride" disclosed in the English abstract is tartaric acid.
Canada 872415 (ESB 1971) discloses a seawater electrolyte battery with a manganese dioxide cathode, and a magnesium or zinc anode. There is no disclosure or suggestion of cuprous chloride or transition metal salt of chalcogen acid constituents of the cathode. Graphite is disclosed as a fabric substrate in a lead dioxide cathode of a cross-referenced application
USSR 160207 (Antonov 1964) discloses production of manganesed metal by electrolysis in a cell with an electrolyte of manganese sulfate, ammonium sulfate, and a small amount of added selenious acid. There is no mention in the English abstract of a cuprous halide ingredient
Chubb U.S. Pat. No. 2,658,935 discloses a magnesium-cuprous chloride "meteorological" or "one-shot" battery in which the cuprous chloride electrode is porous and contains a cuprous chloride paste containing finely ground cuprous chloride, water, and a solution of a high polymer such as polystyrene in an organic solvent, optionally a plasticizer for the polystyrene, and various inert conductive materials added to improve the conductivity of the cuprous chloride such as carbon black or graphite.
There still remains a need for an improved water-activated battery able to activate rapidly in both salt and fresh water and to maintain its ability to power a signal light for extended periods.